This invention relates to a generator for producing high-voltage rectangular pulses with devices for conversion of input power supplied from a DC source into pulses of output power using capacitive storage units and with a pulser head for the connection of a coaxial cable leading to a load (capacitor, antenna, electro-optical switch, electrostatic filter or the like).
High-voltage rectangular pulses are for example required for the testing of insulating materials in solid, liquid or gaseous form. Very precise timing and/or amplitudes are required inter alia for driving electro-optical switches for lasers or the like, for pulsed spark and ionization chambers and for testing of electronic components, modules and equipment. Another field of application, in which stringent requirements are placed on resistance to short-circuiting, and accuracy of pulse shape, i.e. edge steepness and amplitude characteristic, is less important, is electrostatic filtering of waste gases.
So-called Marx generators for instance are sufficiently well known as to not require special reference to the literature. High voltages can be achieved with these. On account of the energy storage unit discharging through the load or bleeder resistors however rectangular pulses of a longer duration cannot be achieved with them. The known cable pulsers according to Fletcher and Blumlein have a coaxial cable to be charged up and a discharge gap or a krytron as the switching device. Long pulses cannot be produced with these since the propagation time in the cable determines their top length. Pulses 25 ms in duration require a cable length of about 2.5 km. Moreover, the cable losses and the dispersion of the wave lead to drooping of the top of the pulse and a poor trailing edge. Pulse circuits with output transformers, on account of the limited core inductance and the consequential exponential decay of the top of the pulse and the negative undershoot of the trailing edge of the output voltage, are unsuitable when the demands are greater.
In spite of the advances in the development of semiconductor devices, transistors and thyristors cannot be considered for the switching device if high switching capacities, high disruptive strength and short switching times are required. Electron tubes as a result of low specific cathode current density are too slow. Large cathode surfaces lead to excessive capacitances of the tube electrodes.